And it actually irks how The Avengers just negates Thor's ending because 1. Loki was fine, 2. Getting back to Earth was no big deal.

Loki was very far from fine - I got an oh sh*********t in the post-credits scene of Thor seeing Loki shadowing Erik. (If I hadn't seen that straight after, and was convinced Loki was dead for a year before seeing the Avengers, maybe I would have had a different reaction.) This is someone who was utterly utterly lost and now dedicated to pure revenge and evil, resonating in a way that someone who hadn't had that kind of almost-sympathetic origin story wouldn't have had.

"Dark energies" sounded pretty ominous to me when I was watching The Avengers. But I get that some found it a fake-out.